|
|
|
|
|
#lang racket/base
|
|
|
|
|
|
(require "helper.rkt" "util.rkt" "number.rkt" "array.rkt" racket/stream racket/dict sugar/unstable/dict)
|
|
|
|
|
|
(provide (all-defined-out))
|
|
|
|
|
|
|
|
|
|
|
|
#|
|
|
|
|
|
|
approximates
|
|
|
|
|
|
https://github.com/mbutterick/restructure/blob/master/src/LazyArray.coffee
|
|
|
|
|
|
|#
|
|
|
|
|
|
|
|
|
|
|
|
(define (xlazy-array-decode xla [port-arg (current-input-port)] #:parent [parent #f])
|
|
|
|
|
|
(define port (->input-port port-arg))
|
|
|
|
|
|
(parameterize ([current-input-port port])
|
|
|
|
|
|
(define starting-pos (pos port)) ; ! placement matters. `resolve-length` will change `pos`
|
|
|
|
|
|
(define decoded-len (resolve-length (xarray-base-len xla) #:parent parent))
|
|
|
|
|
|
(let ([parent (if (xint? (xarray-base-len xla))
|
|
|
|
|
|
(mhasheq 'parent parent
|
|
|
|
|
|
'_startOffset starting-pos
|
|
|
|
|
|
'_currentOffset 0
|
|
|
|
|
|
'_length (xarray-base-len xla))
|
|
|
|
|
|
parent)])
|
|
|
|
|
|
(define starting-pos (pos port))
|
|
|
|
|
|
(define res (for/stream ([index (in-range decoded-len)])
|
|
|
|
|
|
(define type (xarray-base-type xla))
|
|
|
|
|
|
(define orig-pos (pos port))
|
|
|
|
|
|
(pos port (+ starting-pos (* (size type #f #:parent parent) index)))
|
|
|
|
|
|
(define new-item (decode type port #:parent parent))
|
|
|
|
|
|
(pos port orig-pos)
|
|
|
|
|
|
new-item))
|
|
|
|
|
|
(pos port (+ (pos port) (* decoded-len (size (xarray-base-type xla) #f #:parent parent))))
|
|
|
|
|
|
res)))
|
|
|
|
|
|
|
|
|
|
|
|
(define (xlazy-array-encode xla val [port-arg (current-output-port)] #:parent [parent #f])
|
|
|
|
|
|
(xarray-encode xla (if (stream? val) (stream->list val) val) port-arg #:parent parent))
|
|
|
|
|
|
|
|
|
|
|
|
(define (xlazy-array-size xla [val #f] #:parent [parent #f])
|
|
|
|
|
|
(xarray-size xla (if (stream? val) (stream->list val) val) #:parent parent))
|
|
|
|
|
|
|
|
|
|
|
|
;; xarray-base holds type and len fields
|
|
|
|
|
|
(struct xlazy-array xarray-base () #:transparent
|
|
|
|
|
|
#:methods gen:xenomorphic
|
|
|
|
|
|
[(define decode xlazy-array-decode)
|
|
|
|
|
|
(define encode xlazy-array-encode)
|
|
|
|
|
|
(define size xlazy-array-size)])
|
|
|
|
|
|
|
|
|
|
|
|
(define (+xlazy-array type [len #f])
|
|
|
|
|
|
(unless (xenomorphic? type)
|
|
|
|
|
|
(raise-argument-error '+xarray "xenomorphic type" type))
|
|
|
|
|
|
(unless (length-resolvable? len)
|
|
|
|
|
|
(raise-argument-error '+xarray "length-resolvable?" len))
|
|
|
|
|
|
(xlazy-array type len))
|
|
|
|
|
|
|
|
|
|
|
|
(module+ test
|
|
|
|
|
|
(require rackunit "number.rkt")
|
|
|
|
|
|
(define bstr #"ABCD1234")
|
|
|
|
|
|
(define ds (open-input-bytes bstr))
|
|
|
|
|
|
(define la (+xlazy-array uint8 4))
|
|
|
|
|
|
(define ila (decode la ds))
|
|
|
|
|
|
(check-equal? (pos ds) 4)
|
|
|
|
|
|
(check-equal? (stream-ref ila 1) 66)
|
|
|
|
|
|
(check-equal? (stream-ref ila 3) 68)
|
|
|
|
|
|
(check-equal? (pos ds) 4)
|
|
|
|
|
|
(check-equal? (stream->list ila) '(65 66 67 68))
|
|
|
|
|
|
(define la2 (+xlazy-array int16be (λ (t) 4)))
|
|
|
|
|
|
(check-equal? (encode la2 '(1 2 3 4) #f) #"\0\1\0\2\0\3\0\4")
|
|
|
|
|
|
(check-equal? (stream->list (decode la2 (open-input-bytes #"\0\1\0\2\0\3\0\4"))) '(1 2 3 4)))
|
